diff --git a/src/map/IMG/mapdata.h b/src/map/IMG/mapdata.h
index 0e919c53..2fe0303c 100644
--- a/src/map/IMG/mapdata.h
+++ b/src/map/IMG/mapdata.h
@@ -21,7 +21,7 @@ public:
 	struct Poly {
 		/* QPointF insted of Coordinates for performance reasons (no need to
 		   duplicate all the vectors for drawing). Note, that we do not want to
-		   ll2xy() the points in the IMG class as this can not be done in
+		   ll2xy() the points in the MapData class as this can not be done in
 		   parallel. */
 		QVector<QPointF> points;
 		Label label;
@@ -44,15 +44,6 @@ public:
 		  {return id < other.id;}
 	};
 
-	struct Polys {
-		Polys() {}
-		Polys(const QList<Poly> &polygons, const QList<Poly> &lines)
-			: polygons(polygons), lines(lines) {}
-
-		QList<Poly> polygons;
-		QList<Poly> lines;
-	};
-
 	MapData();
 	virtual ~MapData();
 
@@ -87,8 +78,20 @@ protected:
 	QString _errorString;
 
 private:
+	struct Polys {
+		Polys() {}
+		Polys(const QList<Poly> &polygons, const QList<Poly> &lines)
+			: polygons(polygons), lines(lines) {}
+
+		QList<Poly> polygons;
+		QList<Poly> lines;
+	};
+
 	QCache<const SubDiv*, Polys> _polyCache;
 	QCache<const SubDiv*, QList<Point> > _pointCache;
+
+	friend class VectorTile;
+	friend class PolyCTX;
 };
 
 #ifndef QT_NO_DEBUG